On The Parameter Choice for Cyclic Delay Diversity Based Precoding with Spatial Multiplexing
A method called open loop Cyclic Delay Diversity (CDD) precoding has recently become part of the standard for 3GPP Long-Term Evolution (LTE) cellular communications systems. CDD had previously been proposed as single stream diversity method for OFDM systems. The proposal in LTE is an extension to spatial multiplexing using so called large delay CDD. The purpose of this paper is twofold: the authors give two different interpretations of the CDD precoding scheme in LTE as beam switching and transformation of spatial diversity to frequency diversity. They then discuss the impact of the delay parameter in CDD precoding on the achievable rates and BER performance.